Add unit test coverage for the new "expand-recurrences" property on GcalTimeline and GcalCalendarMonitor, ensuring proper propagation, default values, and notify signal emission. Also verify that GcalSearchHitEvent correctly indicates recurrence in hit subtitles. Reference: https://gitlab.gnome.org/GNOME/gnome-calendar/-/issues/991 Part-of: <https://gitlab.gnome.org/GNOME/gnome-calendar/-/merge_requests/808>